Physics

Physics (also spelled Fisikis or Fiisikis) is the natural science that studies matter, energy, space, and time, and how they interact. Its aim is to explain natural phenomena through general laws that can be measured and tested, ranging from the smallest components to the structure of the entire universe.

The method of physics rests on the interaction of observation, experiment, and mathematical description. A theory is evaluated by how well it predicts measurable outcomes; if measurement differs from prediction, the theory is revised or its scope is narrowed. Mathematics is the primary language for explanation.

Major branches

Classical physics comprises Newtonian mechanics, thermodynamics, waves and motion, and electricity and magnetism unified by Maxwell. Modern physics rests on two pillars: Einstein's relativity theory, which studies high-speed motion and gravity, and quantum mechanics, which studies the atomic scale and smaller.

Measurement and units

Physics relies on a system of universal units, such as SI, which includes the metre (length), kilogram (mass), second (time), and ampere (electric current). Each measurement is subject to uncertainty; no reported figure should be taken as complete.

Fundamental forces

At the lowest level, four fundamental forces have been identified: gravity, the electromagnetic force, the strong nuclear force, and the weak nuclear force. Much research attempts to unify these forces into a single framework; so far, gravity and quantum mechanics have not been fully reconciled.